Straw protein feed based on fungal fermentation and preparation method thereof
By modifying the straw substrate and regulating it with polyol metabolism inducers, the problems of dense straw structure and low nitrogen source utilization efficiency were solved, enabling the preparation of high-protein and high-digestibility straw protein feed and improving fungal fermentation efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INNER MONGOLIA UNIV FOR THE NATITIES
- Filing Date
- 2026-01-15
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, straw has a dense structure and is heavily coated with lignin. During fungal fermentation, the accessibility of carbon sources is low and the utilization efficiency of nitrogen sources is not high, resulting in limited improvement in straw protein content and making it difficult to produce high-protein, highly digestible straw protein feed.
By modifying the straw substrate with a composite structure and introducing low-molecular-weight polyol organic compounds as metabolic inducers, the metabolic pathways related to fungal nitrogen metabolism and protein synthesis are regulated, thereby promoting the efficient conversion of exogenous nitrogen sources into microbial proteins.
It significantly improves the crude protein content and digestibility of straw protein feed, enhances fungal fermentation efficiency, and realizes the efficient conversion of straw resources into microbial protein.
Smart Images
Figure CN122004353A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of feed biotechnology and bio-fermentation engineering, specifically relating to a straw protein feed based on fungal fermentation and its preparation method. Background Technology
[0002] With the rapid development of animal husbandry and aquaculture, the demand for protein feed ingredients continues to grow. Traditional feed protein sources mainly rely on plant-based or animal-based protein ingredients such as soybean meal and fishmeal, which are not only costly and highly susceptible to fluctuations in the international market, but also exacerbate competition for food resources and environmental pressures to some extent. Therefore, developing widely available, low-cost, and sustainable alternative protein feed ingredients has become an important research direction in the feed industry and the field of comprehensive utilization of agricultural resources.
[0003] Straw-based agricultural waste, such as corn stalks, wheat stalks, and rice stalks, is produced in huge quantities annually. Its main components are cellulose, hemicellulose, and lignin, possessing potential for resource utilization. However, due to the high lignin content and dense structure of straw, with cellulose tightly coated by lignin, its digestibility is low and its nutritional value limited when used directly as feed, potentially even burdening the animal's digestive system. Currently, straw feed utilization primarily employs methods such as physical crushing, chemical alkali treatment, or simple microbial fermentation, but these methods still generally suffer from insufficient lignin degradation, limited nutritional enhancement, and low protein content.
[0004] Fungal fermentation technology is considered an effective way to improve the nutritional value of straw feed due to its strong ability to degrade cellulose and lignin. Current technologies often use white-rot fungi, Aspergillus, and other microorganisms to ferment straw, increasing crude protein content and improving palatability to some extent through microbial growth and metabolism. However, existing fungal fermentation technologies for straw feed mainly focus on strain selection and optimization of conventional fermentation conditions, with insufficient targeted modification of straw structure and limited means of regulating fungal protein synthesis and metabolism pathways. This results in low nitrogen source utilization efficiency and limited improvement in protein and amino acid content.
[0005] Existing additives used for fermentation regulation are mostly conventional nutrient supplements or inorganic salts, primarily functioning to stabilize the fermentation environment. Their induction of fungal metabolic pathways is weak, making it difficult to significantly increase straw protein content without substantially increasing raw material costs. Therefore, a new technical solution is urgently needed. This solution involves effectively modifying the straw substrate structure and introducing novel metabolic regulation methods during fungal fermentation to achieve efficient conversion of carbon sources in straw into microbial protein, thereby producing high-protein, highly digestible straw protein feed suitable for industrial application. Summary of the Invention
[0006] To overcome the problems in existing technologies, such as the dense structure of straw, severe lignin coating of cellulose, low accessibility of carbon sources, low nitrogen source utilization efficiency, and limited microbial protein synthesis capacity during fungal fermentation, the present invention aims to provide a straw protein feed based on fungal fermentation and its preparation method. This invention improves cellulose accessibility by modifying the composite structure of the straw substrate and introduces specific low-molecular-weight polyol organic compounds as metabolic inducers into the fungal fermentation system. Without the straw acting as a primary carbon source for energy metabolism, this regulates the metabolic pathways related to fungal nitrogen metabolism and protein synthesis, thereby promoting the efficient conversion of exogenous nitrogen sources into microbial proteins and significantly improving the protein content and digestibility of straw feed.
[0007] The objective of this invention can be achieved through the following technical solutions: A straw protein feed based on fungal fermentation, comprising the following raw materials in parts by weight: 60-85 parts modified straw substrate; 0.05-2 parts organic small molecule metabolism inducer; 1-5 parts fungal strain; 2-10 parts nitrogen source; 0.5-3 parts mineral and trace element adjuvants; and 0.1-2 parts fermentation regulator. The modified straw substrate is obtained by physically crushing natural straw and then applying a modifying substance to the surface of straw cellulose / hemicellulose to form weak chemical bonds and intermolecular forces, thereby reducing the effect of lignin on... The degree of cellulose coating and improved cellulose accessibility; the organic small molecule metabolism inducer is selected from at least one of polyol low molecular weight organic compounds, which do not participate in energy metabolism as the main carbon source during fungal fermentation, but can enter the fungal metabolic system, regulate the metabolic pathways related to fungal nitrogen metabolism and protein synthesis, thereby promoting the efficient conversion of exogenous nitrogen source into microbial protein and increasing the crude protein content of the obtained straw protein feed; the fungal strain is a fungus that can degrade cellulose / lignin and has the ability to synthesize protein.
[0008] Optionally, the polyol low-molecular-weight organic compound is selected from one or more of glycerol, ethylene glycol, glycerol, and sorbitol.
[0009] Optionally, the modified straw substrate comprises the following raw materials in parts by weight: 80-95 parts of natural straw; 1-5 parts of modifier; 2-10 parts of polyhydroxy organic modifier; and 1-5 parts of weakly alkaline structure regulator; wherein the modifier is chitosan; the polyhydroxy organic modifier is glycerol; and the weakly alkaline structure regulator is sodium carbonate.
[0010] Optionally, the preparation method of the modified straw substrate includes the following steps: (1) The natural straw is crushed to a particle size of 1-3 mm, and then water is added for soaking to remove surface impurities and fully wet the straw to obtain pretreated straw; (2) Add sodium carbonate aqueous solution to the pretreated straw and treat it under stirring conditions to loosen and break some of the lignin structure in the straw. Then, perform solid-liquid separation to obtain the straw with adjusted structure. (3) Add glycerol to the structure-modified straw and mix and react under certain temperature conditions to form intermolecular forces between glycerol and straw cellulose and / or hemicellulose to obtain polyhydroxy modified straw. (4) Add chitosan to the polyhydroxy modified straw and react it under aqueous conditions so that the modifier interacts with the hydroxyl groups on the surface of the straw to form a product with a stable binding structure. (5) The product is dried, crushed and shaped to obtain modified straw substrate.
[0011] Optionally, the reaction conditions in step (2) are: the mass fraction of sodium carbonate aqueous solution is 0.5-3 wt%, the treatment temperature is 40-80℃, the treatment time is 0.5-3 h, and the reaction is continuously stirred.
[0012] Optionally, the reaction conditions in step (3) are as follows: the amount of glycerol added is 1 to 10% of the mass of straw, the reaction temperature is 50 to 90°C, and the reaction time is 1 to 4 hours.
[0013] Optionally, the reaction conditions in step (4) are as follows: the amount of chitosan added is 0.5-5% of the mass of straw, the reaction temperature is 25-70℃, the reaction time is 0.5-3h, and the reaction system is an aqueous phase.
[0014] Optionally, the nitrogen source is a mixture of urea and ammonium sulfate in a mass ratio of (1-3):(1-2); the mineral and trace element auxiliaries are a mixture of calcium dihydrogen phosphate, magnesium sulfate, zinc sulfate, and ferrous sulfate in a mass ratio of (2-5):(1-3):(0.1-0.5):(0.1-0.5); and the fermentation regulator is a mixture of potassium dihydrogen phosphate and citric acid in a mass ratio of (1-3):(0.5-2).
[0015] Optionally, a method for preparing straw protein feed based on fungal fermentation includes the following steps: S1, the modified straw substrate, nitrogen source, mineral and trace element additives and fermentation regulator are mixed together, and an organic small molecule metabolism inducer is added and mixed thoroughly to obtain the fermentation substrate; S2, add water to the fermentation substrate to adjust its moisture content to 55-70%, then sterilize the fermentation substrate and cool it for later use; S3. Under aseptic conditions, inoculate fungal strains into the cooled fermentation substrate. The inoculation amount is 1-5% of the mass of the fermentation substrate, and mix thoroughly. S4. The inoculated fermentation substrate is placed in a fermentation environment for fermentation. The fermentation temperature, humidity and pH conditions are controlled so that the fungi degrade the modified straw substrate and synthesize microbial proteins under the action of organic small molecule metabolism inducers, and the fermentation products are obtained. S5. After fermentation, the fermentation products are dried, crushed and sieved to obtain the finished straw protein feed based on fungal fermentation.
[0016] Optionally, the reaction conditions for step S2 are: the moisture content of the fermentation substrate is 55-70%, the sterilization temperature is 100-121℃, and the sterilization time is 15-40 min; the reaction conditions for step S3 are: the inoculation amount of fungal strain is 1-5% of the mass of the fermentation substrate, and the inoculation process is carried out under aseptic conditions; the reaction conditions for step S4 are: the fermentation temperature is 20-30℃, the fermentation humidity is 60-70%, the fermentation time is 10-20 days, and the pH of the fermentation system during the fermentation process is 4.5-6.5.
[0017] The beneficial effects of this invention are: This invention introduces a specific organic small molecule metabolic inducer based on straw structural modification. This organic small molecule participates in regulating the nitrogen metabolism and protein synthesis-related metabolic pathways of fungi during fungal fermentation, rather than serving as the main energy or carbon source. This significantly improves the assimilation efficiency of fungi of external nitrogen sources and promotes a higher proportion of the conversion of carbon sources released from straw into microbial proteins and amino acids. As a result, straw fermented feed achieves a significantly higher crude protein increase than existing technologies under the same raw materials and fermentation conditions, demonstrating the unexpected technical effects brought about by metabolic induction. Attached Figure Description
[0018] The invention will now be further described with reference to the accompanying drawings.
[0019] Figure 1 A comparison of the infrared spectra of natural straw and modified straw substrate; Figure 2 This is a comparison chart of the performance test results of samples with different ratios. Detailed Implementation
[0020] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.
[0021] Example 1: This embodiment aims to verify the feasibility of the present invention's technology for preparing straw protein feed based on fungal fermentation when the amount of each raw material and the reaction conditions are all within the lower limit range defined in the claims.
[0022] Preparation steps: S1, Preparation of modified straw substrate (1) The natural straw is crushed to a particle size of 1 mm, and then soaked in water to fully wet the straw to obtain pre-treated straw. (2) Add a sodium carbonate aqueous solution with a mass fraction of 0.5 wt% to the pretreated straw, stir at 40℃ for 0.5 h, and then perform solid-liquid separation to obtain the straw with adjusted structure; (3) Add glycerol to the structure-modified straw at a rate of 1% of the straw mass, and react at 50°C for 1 hour to obtain polyhydroxy modified straw. (4) Add chitosan to the polyhydroxy modified straw at a rate of 0.5% of the straw mass and react at 25°C for 0.5 h in an aqueous phase. (5) The obtained product is dried, crushed and shaped to obtain modified straw substrate; S2, Fermentation substrate construction and moisture content adjustment By weight, 60 parts modified straw substrate, 2 parts nitrogen source, 0.5 parts mineral and trace element adjuvant, 0.1 parts fermentation regulator and 0.05 parts organic small molecule metabolism inducer are thoroughly mixed, and water is added to adjust the moisture content of the fermentation substrate to 55%. S3, sterilization treatment The fermentation substrate obtained in step S2 was sterilized at 100°C for 15 minutes, and then cooled to room temperature for later use. S4, Fungal inoculation and fermentation Fungal strains were inoculated into the cooled fermentation substrate under aseptic conditions. The inoculation amount was 1% of the mass of the fermentation substrate. After being mixed evenly, the substrate was placed in a fermentation environment and fermented at 25°C, 60% relative humidity, and pH 4.5 for 15 days to obtain the fermentation product. S5, Post-processing After fermentation, the fermentation products are dried, crushed, and sieved to obtain the finished straw protein feed based on fungal fermentation.
[0023] Example 2: This embodiment aims to verify the stability and reproducibility of the preparation of straw protein feed by fungal fermentation through the synergistic effect of modified straw substrate and organic small molecule metabolism inducer when the dosage of each raw material component and the reaction conditions are within the intermediate range defined in the claims.
[0024] Preparation steps: S1, Preparation of modified straw substrate (1) Take natural straw and crush it to control its particle size to 2mm. Then add water to soak it so that the straw can fully absorb water and wet it, and remove some surface impurities to obtain pre-treated straw. (2) Add a sodium carbonate aqueous solution with a mass fraction of 1.5 wt% to the pretreated straw and stir continuously at 60°C for 1.5 h to loosen some of the lignin structure in the straw. After the treatment, perform solid-liquid separation to obtain the straw with adjusted structure. (3) Add glycerol to the structure-modified straw obtained in step (2), the amount of glycerol added is 5% of the straw mass, and mix and react at 70℃ for 2.5h to form intermolecular forces between glycerol and straw cellulose and / or hemicellulose to obtain polyhydroxy modified straw. (4) Add chitosan to the polyhydroxy modified straw obtained in step (3). The amount of chitosan added is 2.5% of the straw mass. React at 45°C for 1.5 h under aqueous conditions so that the modifier interacts with the hydroxyl groups on the straw surface to form a stable binding structure. (5) The product obtained in step (4) is dried, then crushed and shaped to obtain the modified straw substrate; Figure 1 The infrared spectra of the straw substrate before and after modification show that the modified sample has a lower infrared spectrum in the range of 3400–3300 cm⁻¹. -1 The –OH stretching vibration peak was significantly enhanced and broadened, indicating that the number of hydroxyl groups and hydrogen bonding in the system were enhanced after the introduction of the polyhydroxyl organic modifier; the 1730 cm⁻¹ peak related to lignin was also observed. -1 and 1500cm -1 The absorption peaks in the vicinity were significantly weakened, indicating that the weakly alkaline treatment effectively weakened the lignin structure. Meanwhile, the absorption peaks in the 1050–1030 cm⁻¹ range were also significantly reduced. -1 The enhanced C–O vibrational peak of the polysaccharide indicates increased cellulose exposure; the peak at 800–780 cm⁻¹... -1 The appearance of new silicon-oxygen bond characteristic peaks in the range proves that the modifier was successfully grafted. The above changes indicate that the modification treatment significantly optimized the molecular structure of straw. S2, Fermentation substrate construction and moisture content adjustment By weight, 72.5 parts of modified straw substrate, 6 parts of nitrogen source, 1.75 parts of mineral and trace element adjuvant, 1.05 parts of fermentation regulator and 1 part of organic small molecule metabolism inducer were mixed and then water was added to adjust the moisture content of the fermentation substrate to 62.5% to obtain a uniform fermentation substrate. S3, sterilization treatment The fermentation substrate obtained in step S2 was placed in a sterilization device and sterilized at 110°C for 25 minutes. After sterilization, the fermentation substrate was cooled to room temperature for later use. S4, Fungal inoculation and fermentation Under aseptic conditions, fungal strains were inoculated into the cooled fermentation substrate at a concentration of 3% of the substrate mass. After thorough mixing, the inoculated substrate was placed in a fermentation environment and fermented at 28°C, 68% relative humidity, and pH 5.5 for 10 days to obtain the fermentation product. S5, Post-processing After fermentation, the fermentation product obtained in step S4 is dried, then crushed and sieved to obtain the finished straw protein feed based on fungal fermentation.
[0025] Example 3: This embodiment aims to verify the applicability of the present invention's technical solution under conditions of deep straw modification and high-intensity fungal protein synthesis, when the dosage of each raw material component and the reaction conditions are all within the upper limit range defined in the claims.
[0026] Preparation steps: S1, Preparation of modified straw substrate (1) The natural straw is crushed to control the particle size to 3mm, and then soaked in water to fully wet the straw to obtain pre-treated straw; (2) Add a 3wt% sodium carbonate aqueous solution to the pretreated straw and stir continuously at 80°C for 3 hours to further loosen the lignin structure in the straw. Then, perform solid-liquid separation to obtain the straw with adjusted structure. (3) Add glycerol to the structure-modified straw obtained in step (2), the amount of glycerol added is 10% of the straw mass, and mix and react at 90℃ for 4h to obtain polyhydroxy modified straw; (4) Add chitosan to the polyhydroxy modified straw obtained in step (3). The amount of chitosan added is 5% of the straw mass. React at 70°C for 3 hours under aqueous conditions to form a modified product with a stable binding structure. (5) The product obtained in step (4) is dried, crushed and shaped to obtain modified straw substrate; S2, Fermentation substrate construction and moisture content adjustment By weight, 85 parts modified straw substrate, 10 parts nitrogen source, 3 parts mineral and trace element adjuvants, 2 parts fermentation regulator, and 2 parts organic small molecule metabolism inducer were thoroughly mixed, and water was added to adjust the moisture content of the fermentation substrate to 70%. S3, sterilization treatment The fermentation substrate obtained in step S2 was sterilized at 121°C for 40 minutes. After sterilization, it was cooled to room temperature for later use. S4, Fungal inoculation and fermentation Fungal strains were inoculated into the cooled fermentation substrate under aseptic conditions. The inoculation amount of fungal strains was 5% of the mass of the fermentation substrate. After mixing evenly, the inoculated fermentation substrate was placed in the fermentation environment and fermented at 30°C, 70% relative humidity, and pH 6.5 for 20 days to obtain the fermentation product. S5, Post-processing After fermentation is complete, the fermentation product obtained in step S4 is dried, crushed and screened to obtain the final straw protein feed product.
[0027] Comparative Example 1: This comparative example aims to verify the effect of simple modification of straw substrate by weakly basic structural adjustment, without the introduction of polyhydroxy organic modification and silane coupling modification, on the effect of fungal fermentation on the preparation of straw protein feed.
[0028] Preparation steps: S1, Preparation of modified straw substrate (1) Take natural straw and crush it to control its particle size to 2mm. Then add water to soak it so that the straw can fully absorb water and wet it, and remove some surface impurities to obtain pre-treated straw. (2) Add a sodium carbonate aqueous solution with a mass fraction of 1.5 wt% to the pretreated straw and stir continuously at 60°C for 1.5 h to loosen some of the lignin structure in the straw. After the treatment, perform solid-liquid separation to obtain the straw with adjusted structure. (3) The straw obtained in step (2) after structural adjustment is directly dried, then crushed and shaped to obtain the straw substrate of Comparative Example 1; S2, Fermentation substrate construction and moisture content adjustment By weight, take 72.5 parts of the straw substrate obtained in step S1, 6 parts of nitrogen source, 1.75 parts of mineral and trace element adjuvant, 1.05 parts of fermentation regulator and 1 part of organic small molecule metabolism inducer and mix them. After mixing evenly, add water to adjust the moisture content of the fermentation substrate to 62.5% to obtain a uniform fermentation substrate. S3, sterilization treatment The fermentation substrate obtained in step S2 was placed in a sterilization device and sterilized at 110°C for 25 minutes. After sterilization, the fermentation substrate was cooled to room temperature for later use. S4, Fungal inoculation and fermentation Under aseptic conditions, fungal strains were inoculated into the cooled fermentation substrate at a concentration of 3% of the substrate mass. After thorough mixing, the inoculated substrate was placed in a fermentation environment and fermented at 28°C, 68% relative humidity, and pH 5.5 for 10 days to obtain the fermentation product. S5, Post-processing After fermentation, the fermentation product obtained in step S4 is dried, then crushed and sieved to obtain the finished straw protein feed.
[0029] Comparative Example 2: This comparative example aims to verify the effect of simple modification of straw substrate by polyhydroxy organic modification, without weak basic structure adjustment and silane coupling modification, on the effect of fungal fermentation to prepare straw protein feed.
[0030] Preparation steps S1, Preparation of modified straw substrate (1) Take natural straw and crush it to control its particle size to 2mm. Then add water to soak it so that the straw can fully absorb water and wet it, and remove some surface impurities to obtain pre-treated straw. (2) Add glycerol to the pretreated straw obtained in step (1). The amount of glycerol added is 5% of the straw mass. Mix and react at 70°C for 2.5 h to allow glycerol to form intermolecular forces with straw cellulose and / or hemicellulose to obtain polyhydroxy modified straw. (3) The polyhydroxy modified straw obtained in step (2) was dried, then crushed and shaped to obtain the straw substrate of Comparative Example 2; S2, Fermentation substrate construction and moisture content adjustment By weight, take 72.5 parts of the straw substrate obtained in step S1, 6 parts of nitrogen source, 1.75 parts of mineral and trace element adjuvant, 1.05 parts of fermentation regulator and 1 part of organic small molecule metabolism inducer and mix them. After mixing evenly, add water to adjust the moisture content of the fermentation substrate to 62.5% to obtain a uniform fermentation substrate. S3, sterilization treatment The fermentation substrate obtained in step S2 was placed in a sterilization device and sterilized at 110°C for 25 minutes. After sterilization, the fermentation substrate was cooled to room temperature for later use. S4, Fungal inoculation and fermentation Under aseptic conditions, fungal strains were inoculated into the cooled fermentation substrate at a concentration of 3% of the substrate mass. After thorough mixing, the inoculated substrate was placed in a fermentation environment and fermented at 28°C, 68% relative humidity, and pH 5.5 for 10 days to obtain the fermentation product. S5, Post-processing After fermentation, the fermentation product obtained in step S4 is dried, then crushed and sieved to obtain the finished straw protein feed.
[0031] Comparative Example 3: This comparative example aims to verify the effect of fungal fermentation on the protein synthesis of straw protein feed when the straw substrate is modified in the same way as in Example 2, without the addition of organic small molecule metabolism inducers.
[0032] Preparation steps: S1, Preparation of modified straw substrate (1) Take natural straw and crush it to control its particle size to 2mm. Then add water to soak it so that the straw can fully absorb water and wet it, and remove some surface impurities to obtain pre-treated straw. (2) Add a sodium carbonate aqueous solution with a mass fraction of 1.5 wt% to the pretreated straw and stir continuously at 60°C for 1.5 h to loosen some of the lignin structure in the straw. After the treatment, perform solid-liquid separation to obtain the straw with adjusted structure. (3) Add glycerol to the structure-modified straw obtained in step (2), the amount of glycerol added is 5% of the straw mass, and mix and react at 70℃ for 2.5h to form intermolecular forces between glycerol and straw cellulose and / or hemicellulose to obtain polyhydroxy modified straw. (4) Add chitosan to the polyhydroxy modified straw obtained in step (3). The amount of chitosan added is 2.5% of the straw mass. React at 45°C for 1.5 h under aqueous conditions so that the modifier interacts with the hydroxyl groups on the straw surface to form a stable binding structure. (5) The product obtained in step (4) is dried, then crushed and shaped to obtain the modified straw substrate; S2, Fermentation substrate construction and moisture content adjustment By weight, 72.5 parts of modified straw substrate, 6 parts of nitrogen source, 1.75 parts of mineral and trace element adjuvants and 1.05 parts of fermentation regulator are mixed together without adding organic small molecule metabolism inducers. After mixing evenly, water is added to adjust the moisture content of the fermentation substrate to 62.5% to obtain a uniform fermentation substrate. S3, sterilization treatment The fermentation substrate obtained in step S2 was placed in a sterilization device and sterilized at 110°C for 25 minutes. After sterilization, the fermentation substrate was cooled to room temperature for later use. S4, Fungal inoculation and fermentation Under aseptic conditions, fungal strains were inoculated into the cooled fermentation substrate at a concentration of 3% of the substrate mass. After thorough mixing, the inoculated substrate was placed in a fermentation environment and fermented at 28°C, 68% relative humidity, and pH 5.5 for 10 days to obtain the fermentation product. S5, Post-processing After fermentation, the fermentation product obtained in step S4 is dried, then crushed and sieved to obtain the finished straw protein feed.
[0033] Performance testing: 1. Crude protein content test method Straw protein feed samples prepared in Examples 1, 2, and 3, as well as Comparative Examples 1 to 3, were pretreated under the same conditions. Each sample was dried at a constant temperature until its mass became constant, then pulverized and sieved to ensure uniform particle size. Subsequently, the total nitrogen content of each sample was determined using conventional feed industry methods, and the crude protein content of the corresponding sample was obtained accordingly. Multiple parallel tests were performed on each group of samples, and the average value was taken as the final result to compare the differences in protein enrichment capacity between different examples and comparative examples.
[0034] 2. Protein digestibility test method The straw protein feed samples obtained in Examples 1, 2, and 3, and Comparative Examples 1 to 3 were pulverized and sieved, respectively. The protein digestibility of the samples was then evaluated using an in vitro simulated digestion method. During the test, the samples were first placed in a simulated gastric juice environment for digestion, and then transferred to a simulated intestinal juice environment for further digestion, thus simulating the digestion process of feed in the animal's digestive tract. After digestion, the digestive residue was analyzed and compared with the undigested sample to evaluate the level of protein digestibility and utilization in the straw protein feed under different technical schemes.
[0035] 3. Nitrogen source utilization efficiency test method Under the same nitrogen source addition and fermentation conditions, fermentation systems corresponding to Examples 1, 2, 3, and Comparative Examples 1 to 3 were subjected to fermentation treatment. After fermentation, the state of residual nitrogen source in the fermentation products was detected, and the degree of nitrogen source conversion to microbial protein during fermentation was analyzed in conjunction with the changes in crude protein content in the final feed. By comparing the nitrogen source utilization in different samples, the effects of modified straw substrate and organic small molecule metabolism inducers on fungal nitrogen assimilation efficiency were evaluated.
[0036] 4. Methods for testing fungal growth and overall fermentation efficiency At the end of fermentation, samples of the fermentation products from Examples 1, 2, and 3, as well as Comparative Examples 1 to 3, were taken to analyze the fungal growth. By measuring the microbial-related indicators in the fermentation products, and combining the changes in substrate quality before and after fermentation with the fermentation status during the fermentation cycle, the growth activity of fungi and the overall fermentation efficiency under different technical schemes were comprehensively evaluated, thereby reflecting the differences in fermentation performance between each example and the comparative examples.
[0037] Table 1 Performance Test Results
[0038] According to Table 1 and Figure 2 As shown, there are significant differences in crude protein content between the different examples and the comparative examples. Example 2 has the highest crude protein content, reaching 21.6%, which is significantly higher than 17.8% in Example 1 and 19.9% in Example 3, and also significantly higher than 14.2%–16.0% in Comparative Examples 1–3. This result indicates that under moderate modification intensity and fermentation conditions, the modified straw substrate and the organic small molecule metabolism inducer can synergistically promote the conversion of carbon and nitrogen sources by fungi, resulting in a more complete enrichment of microbial protein; while the protein enhancement effect of the comparative examples is significantly limited due to the lack of key modification steps or the absence of the organic small molecule metabolism inducer.
[0039] Based on the protein digestibility results, the examples were generally superior to the comparative examples. Specifically, Example 2 achieved a protein digestibility of 71.4%, significantly higher than Example 1's 63.5% and Example 3's 67.8%, while the comparative examples 1-3 only achieved 52.6%-57.9%. This indicates that the straw protein feed obtained through compound modification and fermentation under metabolic induction conditions has a protein structure more conducive to digestion and utilization. In contrast, while single modification or the lack of metabolic induction improved the straw structure to some extent, the improvement in protein digestibility remained limited.
[0040] Regarding nitrogen source utilization efficiency, Example 2 also demonstrated the best performance, achieving a nitrogen source utilization efficiency of 68.9%, significantly higher than the 58.2% of Example 1 and 63.4% of Example 3, while the comparative examples were only at a lower level of 44.8%–49.6%. This result indicates that organic small-molecule metabolism inducers effectively promote the assimilation and conversion of exogenous nitrogen sources into microbial proteins during fungal fermentation, while simply relying on straw structure modification is insufficient to achieve efficient regulation of fungal nitrogen metabolism pathways.
[0041] The fungal biomass results show that Example 2 exhibited the highest fungal biomass at 128 g / kg dry basis, significantly higher than Example 1's 92 g / kg and Example 3's 110 g / kg, and also significantly higher than the comparative proportions. This result further confirms that, under suitable modification and fermentation conditions, organic small-molecule metabolism inducers can enhance fungal growth activity and metabolic levels, thereby improving overall fermentation efficiency.
[0042] In summary, this invention, through the composite modification of straw substrate and the introduction of organic small molecule metabolic inducers, achieves effective synergistic regulation of protein synthesis and nitrogen source utilization during fungal fermentation. The resulting straw protein feed is significantly superior to the comparative example in terms of crude protein content, protein digestibility, nitrogen source utilization efficiency, and fungal growth. Among them, Example 2 exhibits the best comprehensive performance, fully demonstrating the inventiveness and superiority of the technical solution of this invention.
Claims
1. A straw protein feed based on fungal fermentation, characterized in that, The straw protein feed comprises the following raw materials in parts by weight: 60-85 parts modified straw substrate; 0.05-2 parts organic small molecule metabolism inducer; 1-5 parts fungal strain; 2-10 parts nitrogen source; 0.5-3 parts mineral and trace element adjuvant; and 0.1-2 parts fermentation regulator. The modified straw substrate is obtained by physically crushing natural straw and then applying a modified substance to the surface of straw cellulose / hemicellulose to form weak chemical bonds and intermolecular forces, thereby reducing the degree of lignin coating on cellulose and improving cellulose accessibility. The organic small molecule metabolism inducer is selected from at least one of polyol low-molecular-weight organic compounds. These polyol low-molecular-weight organic compounds do not participate in energy metabolism as a major carbon source during fungal fermentation but can enter the fungal metabolic system, regulating the metabolic pathways related to fungal nitrogen metabolism and protein synthesis, thereby promoting the efficient conversion of exogenous nitrogen sources into microbial protein and increasing the crude protein content of the resulting straw protein feed. The fungal strain is a fungus capable of degrading cellulose / lignin and possessing protein synthesis capabilities.
2. The straw protein feed based on fungal fermentation according to claim 1, characterized in that, The polyol low-molecular-weight organic compounds are selected from one or more of glycerol, ethylene glycol, glycerol, and sorbitol.
3. The straw protein feed based on fungal fermentation according to claim 1, characterized in that, The modified straw substrate comprises the following raw materials in parts by weight: 80-95 parts of natural straw; 1-5 parts of modifier; 2-10 parts of polyhydroxy organic modifier; and 1-5 parts of weakly alkaline structure regulator; wherein the modifier is chitosan; the polyhydroxy organic modifier is glycerol; and the weakly alkaline structure regulator is sodium carbonate.
4. A straw protein feed based on fungal fermentation according to any one of claims 1 to 3, characterized in that, The method for preparing the modified straw substrate includes the following steps: (1) The natural straw is crushed to a particle size of 1-3 mm, and then water is added for soaking to remove surface impurities and fully wet the straw to obtain pretreated straw; (2) Add sodium carbonate aqueous solution to the pretreated straw and treat it under stirring conditions to loosen and break some of the lignin structure in the straw. Then, perform solid-liquid separation to obtain the straw with adjusted structure. (3) Add glycerol to the structure-modified straw and mix and react under certain temperature conditions to form intermolecular forces between glycerol and straw cellulose and / or hemicellulose to obtain polyhydroxy modified straw. (4) Add chitosan to the polyhydroxy modified straw and react it under aqueous conditions so that the modifier interacts with the hydroxyl groups on the surface of the straw to form a product with a stable binding structure. (5) The product is dried, crushed and shaped to obtain modified straw substrate.
5. A straw protein feed based on fungal fermentation according to claim 3, characterized in that, The reaction conditions for step (2) are: the mass fraction of sodium carbonate aqueous solution is 0.5-3 wt%, the treatment temperature is 40-80℃, the treatment time is 0.5-3 h, and the reaction is continuously stirred.
6. A straw protein feed based on fungal fermentation according to claim 3, characterized in that, The reaction conditions for step (3) are as follows: the amount of glycerol added is 1-10% of the straw mass, the reaction temperature is 50-90℃, and the reaction time is 1-4h.
7. A straw protein feed based on fungal fermentation according to claim 3, characterized in that, The reaction conditions for step (4) are as follows: the amount of chitosan added is 0.5-5% of the mass of straw, the reaction temperature is 25-70℃, the reaction time is 0.5-3h, and the reaction system is aqueous.
8. A straw protein feed based on fungal fermentation according to claim 1, characterized in that, The nitrogen source is a mixture of urea and ammonium sulfate in a mass ratio of (1-3):(1-2); the mineral and trace element auxiliaries are a mixture of calcium dihydrogen phosphate, magnesium sulfate, zinc sulfate, and ferrous sulfate in a mass ratio of (2-5):(1-3):(0.1-0.5):(0.1-0.5); and the fermentation regulator is a mixture of potassium dihydrogen phosphate and citric acid in a mass ratio of (1-3):(0.5-2).
9. A method for preparing straw protein feed based on fungal fermentation, characterized in that, The preparation method includes the following steps: S1, the modified straw substrate, nitrogen source, mineral and trace element additives and fermentation regulator are mixed together, and an organic small molecule metabolism inducer is added and mixed thoroughly to obtain the fermentation substrate; S2, add water to the fermentation substrate to adjust its moisture content to 55-70%, then sterilize the fermentation substrate and cool it for later use; S3. Under aseptic conditions, inoculate fungal strains into the cooled fermentation substrate. The inoculation amount is 1-5% of the mass of the fermentation substrate, and mix thoroughly. S4. The inoculated fermentation substrate is placed in a fermentation environment for fermentation. The fermentation temperature, humidity and pH conditions are controlled so that the fungi degrade the modified straw substrate and synthesize microbial proteins under the action of organic small molecule metabolism inducers, and the fermentation products are obtained. S5. After fermentation, the fermentation products are dried, crushed and sieved to obtain the finished straw protein feed based on fungal fermentation.
10. A method for preparing straw protein feed based on fungal fermentation according to claim 9, characterized in that, The reaction conditions for step S2 are: the moisture content of the fermentation substrate is 55-70%, the sterilization temperature is 100-121℃, and the sterilization time is 15-40 min; the reaction conditions for step S3 are: the inoculation amount of fungal strain is 1-5% of the mass of the fermentation substrate, and the inoculation process is carried out under aseptic conditions; the reaction conditions for step S4 are: the fermentation temperature is 20-30℃, the fermentation humidity is 60-70%, the fermentation time is 10-20 days, and the pH of the fermentation system during the fermentation process is 4.5-6.5.